John Tucker Must Die (2006)

Kate (Brittany Snow) is the new girl in school. She catches John Tucker (Jesse Metcalfe) dating three different girls at once: Carrie - the smart girl, Heather - the cheerleader, and Beth - the activist slut; none of them are aware that they are not the only girl in John's heart. Kate, having been raised by a single mother, has seen the pain caused by playboys like John Tucker, and she won't stand idly by. Together with the three jilted ex-girlfriends, they hatch a plan to teach John a lesson. Things rarely go as planned, especially when Kate starts to think that she might be falling for John herself.